1. Field of the Invention
The present invention relates to an organic luminous material and an organic light-emitting device and, more particularly, an organic luminous material and an organic light-emitting device like an organic electroluminescence (EL) device employing such material.
2. Description of the Prior Art
In recent years, the research and development of the organic EL device applied to the flat display panel, the mobile display device, etc. is vigorously pursued. The display device employing the organic EL device can provide the high brightness and full color display by the low voltage driving.
In addition, the display device consisting of the organic EL devices has features different from the liquid crystal display (LCD). For example, there can be provided the light weight and low cost product that has no viewing angle dependence because it is the spontaneously emissive display, does not need the back lights because of the high contrast, has a quick response speed, has the easy film formation characteristic, and stands the impact since the overall device is constructed by the solid state elements.
The organic EL device has a structure in which the lower electrode formed of transparent conductive material, the organic thin film (luminous layer), and the upper electrode formed of magnesium, potassium, etc. are formed in sequence on the glass substrate, for example, and a thickness of the overall structure can be reduced up to about several mm. Then, the light is emitted from the luminous layer by applying the DC voltage between the lower electrode and the upper electrode, and this light is passed through the lower electrode and the glass substrate to output to the outside. The organic EL device is the injection electroluminescence device that increases the number of carriers in operation by injecting the carriers from the electrode to thus emit the light by the recombination. Sometimes the organic EL device is also called the organic LED.
As the luminous material employed in the organic thin film of the organic EL device, there are the monomer material and the polymer material. Normally the film of the monomer material is formed by the vacuum evaporation method, and normally the film of the polymer material is formed by the coating method. The coating method is practical in device formation because the expensive equipment is not needed.
It is known that PPV (poly p-phenylenevinylene) is employed as the polymer material. The EL device employing such material is set forth in Patent Application Publication (KOKAI) Hei 10-326675, for example.
The conjugated polymer material such as PPV employed as the luminous layer in the prior art is in the high crystallinity state at the normal temperature, unlike the normal polymer material.
Accordingly, if such conjugated polymer material is formed on the substrate, unevenness is ready to occur on the surface of the luminous layer made of the polymer.
If the voltage is applied between the lower electrode and the upper electrode under the condition that the unevenness is present on the surface of the luminous layer, the electric field is ready to concentrate in the concave portion of the surface of the luminous layer. Thus, there is the possibility that the luminous layer is destroyed by the electric field, and then short-circuit between the lower electrode and the upper electrode is caused.
Also, since the luminous layer polymer in the prior art, which is ready to crystallize, is insoluble in the organic solvent, any treatment must be applied, e.g., the polymer must be mixed into the organic solvent while heating, when the polymer is coated on the substrate, and thus it is not easy to handle the polymer. In addition, even if the conjugated polymer in the prior art is solved in the organic solvent, such polymer is still ready to crystallize after the cooling.